1. Field of the Invention
The present invention relates to pumps for pumping hazardous fluids. In particular, the present invention relates to a pump having a split driveshaft consisting of two coaxial shafts connected by a releasable coupling. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR 18035 between the U.S. Department of Energy and Westinghouse Savannah River Company.
2. Discussion of Background
Pumps are widely used in industry to handle liquids and slurries. Many times these liquids and slurries contain radioactive or hazardous materials, including toxic, explosive, or combustible materials, or mixed radioactive and hazardous materials. Presently-available pumps are single shaft designs, that is, an impeller is operatively connected to the pump motor via a single, unitary driveshaft. These designs increase the difficulty in performing maintenance on the pump motor and other sections of the pump because single shafts are typically self-lubricating, that is, the fluid being pumped serves as the lubrication fluid for the shaft bearings, it inevitably contaminates much of the pump. Even for designs that use grease-lubricated bearings, the possibility of the spread of contamination exists.
To limit personnel exposure to hazardous materials, some pumps are designed to be serviced by remotely controlled manipulators or robots, often requiring modification of designs to accommodate remote servicing limitations. If the pump is to be serviced manually, it must first be removed from the installation and decontaminated. Whether done remotely or manually following decontamination, cleaning and servicing contaminated equipment is time-consuming and very costly. Downtime, higher labor cost, and the possibility of personnel exposure to hazardous materials, all contribute to cost. In the case of equipment used in nuclear facilities, the radiation exposure in removing the contaminated equipment can be high, and radiation exposure standards limit the amount of time workers can spend in a radioactive environment.
A number of methods are available for coupling a motor shaft and a pump driveshaft (Haentjens, U.S. Pat. No. 4,854,828; Mayo, U.S. Pat. No. 2,839,006; Pardieck, U.S. Pat. No. 3,771,926), but these are designed to transfer not only torsional forces but axial forces as well and are therefore somewhat complex and more difficult to remove for servicing. Slingers (Haentjens, U.S. Pat. No. 3,163,117; Mayo, U.S. Pat. No. 2,839,006) and cover plates (Pardieck, U.S. Pat. No. 3,771,926) are used to help seal or isolate the pumped fluid from the upper portion of the pump assembly. Pump constructions may prevent the escape of pumped fluids (Zehnder, et al., U.S. Pat. No. 4,875,836), and allow quick removal and replacement of the pump's motor (Baker, U.S. Pat. No. 3,179,827). However, there are no pumps currently available that are designed to minimize contamination of the high-maintenance portions of the pump, and to minimize personnel exposure to hazardous constituents of the fluid during operation and maintenance.